The most common and most likely answer to this crossword clue is the 7 letter word SWELTER
I've seen this crossword clue in The Times
S
W
E
L
T
E
R
Buddy explains!

The straight part
We know that "feel hot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case feel hot = swelter.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SWELTER mean?
SWELTER noun- Intense heat.
- To suffer terribly from intense heat.
- To perspire greatly from heat.
- To cause to faint, to overpower, as with heat.